Well first test is a fail. I hooked up one of the secondary regulators alone with the pass through plugged and my pressure tester hooked up to the check valve outlet last night. This morning both gauges were registering a drop in pressure! I had sprayed all connections with soapy water and witnessed no bubbling.
I even used special gas teflon tape I found at the hardware store. I had not seen that before. It is thicker and less stretchy/flimsy with a slightly yellow tinge to it. It is intended for use with propane, natural gas etc. so I figure it was good for this purpose.
I am thinking I may and try opening up one of the secondary regulators today to see what I can see. Never done that before so I may be sacrificing the regulator as it may get damaged...
One other possibilty I am considering is that the gauges themselves are leaking? As I was reassembling the secondaries (rewrapped the threads and put gauges, and fittings back on) one of the gauges got damaged somehow and is no reading 8 psi all the time. I started another thread inquiring about gauges.